Keying device for ultra-short-wave transmitters



April 8, 1941. ERNST 2,237,661

KEYING DEVICEFOR ULTRA-SHCRT-WAVE,TRANSMITTERS Filed Nov. 18, 1938 2Sheets-Sheet 1 Fig.1

3 2 5 I 4 645 3* 7 4 i [8 c T a INVENTOR wars/v BY w lfsiww ATTORN EYApril 8, 1941. G. ERNST 2.237.661

KEYING DEV-ICE FOR ULTRA-SHORT-WAVE TRANSMITTERS Filed Nov. 18, 1958 2Sheets-Sheet 2 '0- 'l i I l l 60/1111- K H I z l Fig.5

U I I f 5' 100000 SEC 3 $10 550. H A

ll IYVVIvv AAAAAAA vvvvvvv INVENTOR GERT ERN T ATTORNEY Patented Apr. 8,1941 KEYHJG DEVICE FOR ULTRA-SHORT-WAVE TRANSMITTE'RS Gert Ernst,Berlin, Germany; assignor to Siemens lipparateund Maschinen Gesellschaftmit be- .schrankter .Illaftung, Berlin, Germamga corporation of GermanyApplication November 18, 1938,Serial No. 241,166 In Germany October 7,1937 1 Claim.

The oinventionis concerned with ways and means adapted to produceextremely brief impulses and serving to key modulate an ultrashort wavetransmitter.

Accordingto former practice it has been customary to produce theimpulses required for keying transmitters 'by the aid of grid-controlledgas or vapor-filled discharge tubes or discharge tubes WithOllll'SllChcontrol. However, discharge tubes of this kind involve the drawback thatthey are useful only up toa certain frequency,

on the ground that, beyond such frequency limit,

the impulses experience a certain wear, that is, become blurred. On theother hand, however, the tendency in modern art is to operate with evenshorter waves in many fields and for many purposes, and for these,arrangements as known in the prior art are no longer usable.

The present invention has the aim and object to create a keying deviceadapted to ultrashort-wave transmitters so that an amplifier tube, say,a triode, a pentode or the like, may be employed, which, by the aid of asinusoidal potential, is overloaded, and that as a result the platecurrent being of rectangular shape is differentiated by the aid of atransformer.

Further details of the invention flow from the following more detaileddescription thereof by reference to the appended drawings, in which:

Figure 1 is a circuit organization for a keying device as heredisclosed;

Figures 2 to 5 illustrate the shape of current and potential in acircuit organization as shown in the exemplified embodiment;

Figure 6 shows the same circuit arrangement as in Figure l to whicharr-amplifying stage has been added.

Referring to the circuit organization shown in Figure 1, l denotes anamplifier tube which in the present embodiment consists of a powerpentode whose grid is fed with a sinusoidal potential by way of an inputtransformer 3 and an ohmic resistance 2. In parallel. relationship tothe grid of said pentode I is a diode 4, the cathode of which haspreferably a negative potential with reference to the cathode of thepentode. During the positive alternations, the said diode constitutesand acts as a short-circuit with reference to the series resistance 2and prevents any undue growth of the grid potential and thus of theplate current of pentode I. The plate circuit includes a transformer 5,preferably of the iron cored radio frequency type, the secondary windingof which delivers the brief impulses. In parallel relation totransformer 5, a r

damping resistance indicated at 6 and 1, respectively, is connected bothatthe primary -and at the secondary end.

The operation of this exemplified embodiment will now be demonstrated bythe use of a numerical example. Suppose the sinusoidal potential herefurnished is 200 v., at 15 kc., and that resistance 2 has a value of 200k.-ohm. Owing to the fact that diode i, during the negative alternation,has an infinitely high resistance, Whereas its resistance, upon passagethrough zero to the positive alternation, inside a range of around2-v.,decreases to 1.5 k .-ohm, it causes in the positive alternation a markeddrop of potential across the resistance 2. The shape of the potentialbetween cathode and anode of diode 4 is shown in Figure 2. The anode ofthe diode is now connected with the grid of the power pentode I, thefilament of which, by the aid of a battery 8, is maintained about 10 v.higher than the cathode of the said diode. The potential at the grid ofthe pentode then assumes a shape such as shown in Figure 3. Owing tomarked overrunning or overloading the shape of the plate current of thepentode is rectangular as illustrated in Figure 4. The U -Jacharacteristic of the pentode is covered inside a period of time equalto 18 volts (See Figure 5.)

since transformer 5 by the action of this voltage impulse would becaused to oscillate at its natural wave, damping means are provided inthat both at the primary and the secondary end of the transformer theresistances 6 and 7 each of 7.5 ln-ohm are connected in parallel. The

identical effect would be obtainable by means of a single resistanceabout one-half the said size and connected either at the primary end orat the secondary end. As a consequence, the impulse potential drops toaround 10 v. However, inasmuch as this potential is inadequate forkeying an ultra-short-wave transmitter, an amplifier is added to theoutfit illustrated in Figure 1. This circuit organization is shown inFigure 6 in which such parts as are shown also in Figure 1 are denotedby identical reference numerals. It will be seen that the impulsepotential put out at the secondary end of the transformer 5 is impressedupon the grid of an amplifier tube 9 in which it is amplified to around60 to 80 v. Contradistinct to the circuit scheme shown in Fi ure 1, thepotential of the cathode of the diode tube which is negative in relationto the cathode potential of the pentode is automatically produced inthat resistance 10 and a condenser H are included in the cathode lead ofthe pentode I.

In case it is found that the impulses generated with this arrangementare not short enough, then the length of the impulses may be stillfurther abbreviated to an appreciable extent by repeated differentiationof the plate current of the amplifier stage by the aid of anothertransformer of suitable dimensions, which has not been shown in thedrawings.

Ultra-short-Wave transmitters of this nature which are keyed by a deviceas hereinbefore disclosed are, for instance, used to advantage inconnection with electrical altimeters which are predicated for theiroperation upon echo and reflection of signals. As known from practice,if perfect measuring results are to be obtained, it is necessary thatthe duration of the transmitted impulse should be short compared withits travel or transit time. Another practical field of application forthe scheme of the invention is in connection with impulsedirection-finding work.

In short, it will be evident that the arrangement of the invention maybe usefully adopted wherever ultra-short-waves are used in practice.

What is claimed is:

In a system for generating impulses of a definite duration separated byintervals of a definite duration, an electron discharge device having ananode, a cathode and a control grid, a reactor, means for impressingalternating current voltages on said reactor, a resistance in serieswith said reactor connected between said control grid and cathode, adiode rectifier having an anode and a cathode, means connecting saidrectifier anode to cathode impedance in shunt to said series reactor andresistance whereby voltages alternate half cycles of which are ofdifierent amplitude are set up on the anode and cathode of saidrectifier, means connecting the anode of said rectifier to the controlgrid of said device, a source of potential having its positive terminalconnected to the cathode of said device and its negative terminalconnected to the cathode of said diode rectifier, said source ofpotential biasing said diode cathode relative to the cathode of saiddevice by an amount sufficient to substantially cut off the positiveportion of the cycles of said sinusoidal potentials, a, transformerhaving a primary winding connected to the anode of said device and asecondary winding from which impulses initiated by the negative portionsof the cycles of said sinusoidal potentials only may be derived, andresistances in shunt to the primary and secondary windings of saidtransformer.

GERT ERNST.

